So the guy next door let me use his Cub Cadet rider to cut the yard and I decided to check the oil .. What oil? .. Bone dry so all I had was a quart plus of Shell RTS 5w40 synthetic. The motor is a Koler Courage I think around 18hp and it took just over a quart. Was this the wrong oil to add? Did I just trash this guys rider with the wrong oil?